```html
<!DOCTYPE html>
<html lang="zh-CN">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>联合索引深度解析 | 数据库性能优化</title>
    <link rel="stylesheet" href="https://cdn.staticfile.org/font-awesome/6.4.0/css/all.min.css">
    <link rel="stylesheet" href="https://cdn.staticfile.org/tailwindcss/2.2.19/tailwind.min.css">
    <link href="https://fonts.googleapis.com/css2?family=Noto+Serif+SC:wght@400;500;600;700&family=Noto+Sans+SC:wght@300;400;500;700&display=swap" rel="stylesheet">
    <script src="https://cdn.jsdelivr.net/npm/mermaid@latest/dist/mermaid.min.js"></script>
    <style>
        body {
            font-family: 'Noto Sans SC', Tahoma, Arial, Roboto, "Droid Sans", "Helvetica Neue", "Droid Sans Fallback", "Heiti SC", "Hiragino Sans GB", Simsun, sans-serif;
            color: #333;
            line-height: 1.8;
        }
        h1, h2, h3, h4 {
            font-family: 'Noto Serif SC', serif;
            font-weight: 700;
        }
        .hero-gradient {
            background: linear-gradient(135deg, #6e8efb 0%, #a777e3 100%);
        }
        .card-hover {
            transition: all 0.3s ease;
        }
        .card-hover:hover {
            transform: translateY(-5px);
            box-shadow: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
        }
        .first-letter {
            float: left;
            font-size: 3.5rem;
            line-height: 3.5rem;
            padding-top: 0.5rem;
            padding-right: 0.5rem;
            font-weight: 700;
            color: #4f46e5;
        }
        .divider {
            border: none;
            height: 1px;
            background: linear-gradient(to right, transparent, rgba(156, 163, 175, 0.5), transparent);
            margin: 2rem 0;
        }
    </style>
</head>
<body class="bg-gray-50">
    <!-- Hero Section -->
    <section class="hero-gradient text-white py-20 px-4 md:px-0">
        <div class="container mx-auto max-w-5xl px-4">
            <div class="flex flex-col items-center text-center">
                <h1 class="text-4xl md:text-5xl font-bold mb-6">联合索引的底层实现与优化</h1>
                <p class="text-xl md:text-2xl max-w-3xl opacity-90 mb-8">探索B+树如何赋能数据库性能，解密复合索引的最佳实践</p>
                <div class="flex items-center space-x-2">
                    <span class="px-3 py-1 bg-white bg-opacity-20 rounded-full text-sm"><i class="fas fa-database mr-1"></i> 数据库优化</span>
                    <span class="px-3 py-1 bg-white bg-opacity-20 rounded-full text-sm"><i class="fas fa-chart-line mr-1"></i> 性能提升</span>
                </div>
            </div>
        </div>
    </section>

    <!-- Main Content -->
    <main class="container mx-auto max-w-5xl px-4 py-12">
        <!-- Intro Section -->
        <section class="mb-16">
            <div class="flex items-start mb-8">
                <div class="first-letter">联</div>
                <p class="text-lg text-gray-700">
                    合索引的底层实现通常基于 B+ 树，其结构包括内节点和叶子